The present invention relates to ink cartridges used for supplying liquid ink to a printhead in a thermal ink jet printing apparatus. Specifically, the present invention relates to structure and method for improving the flow of ink and air through an ink cartridge to provide improved ink delivery to the ink jet printing apparatus.
The principles of thermal ink jet printing are well understood in the art. U.S. Pat. No. 5,997,121 describes several aspects of such printing. In existing thermal ink jet printing, the printhead comprises one or more ink filled channels communicating with a relatively small supply chamber, or manifold, at one end, and having an opening at the opposite end, referred to as a nozzle. Current practical embodiments of drop on demand thermal ink jet printers work most effectively when the pressure of the ink in the printhead nozzle remains within a predetermined range of gauge pressures. Specifically, at those times during operation in which an individual nozzle or an entire printhead is not actively emitting a droplet of ink, a certain negative pressure, or xe2x80x9cback pressurexe2x80x9d, in each of the nozzles, and by extension, within the ink supply manifold of the printhead keeps the ink from dribbling out the nozzles. The attributes of creating and maintaining such back pressure are described in U.S. Pat. No. 5,289,212, the contents of which are hereby incorporated herein by reference.
The liquid ink is supplied to the printhead from an ink cartridge. The ink cartridge contains a supply of ink, and is typically configured to maintain the appropriate negative pressure in the printhead ink channels. The ink cartridge is typically a user replaceable unit that mates with the printhead of the printing apparatus. In certain embodiments, the printhead and the ink cartridge are formed as a single integrated unit. In other embodiments, the ink cartridge or container is manufactured and sold separately from the printhead. The printhead may be permanently installed in the printer, or may be separately replaceable.
A fluid cartridge for dispensing fluid, such as liquid ink in a drop on demand ink jet printer, includes a housing that encloses a foam chamber, and has an outlet port through one wall of the housing into the foam chamber. Foam material is contained within the foam chamber. The foam material has a higher density adjacent the outlet port than away from the port.
An ink cartridge for dispensing liquid ink to a drop on demand ink jet printer comprises a housing having a top wall, a plurality of sidewalls, and a cover wall, all enclosing an interior space. The top wall and the cover wall oppose one another across the interior space. A divider separates the interior space into a foam chamber and a free ink chamber. A fluid conduit connects the free ink chamber and the foam chamber. Ink-retaining foam material is contained in the foam chamber. An outlet port through the cover wall extends into the foam chamber. First and second structural projections extend from the top wall of the housing into the foam chamber. The first and second structural projections abut the foam material in the foam chamber. The first structural projection is approximately opposite the outlet port through the cover wall, and extends farther into the foam chamber than does the second structural projection.
A method of assembling an ink cartridge for a drop on demand ink jet printer includes supplying a housing having a plurality of walls defining an interior space, and having one side of the housing open to provide access to the interior space. The method further includes compressing ink retaining foam, and inserting the compressed ink retaining foam through the open side of the housing into the interior space of the housing, so that a first portion of the foam in the interior space of the housing is more compressed than a second portion of the foam in the interior space of the housing. A cover wall is applied over the open side of the housing to enclose the foam in the interior space of the housing. In a particular implementation, the cover wall has a port through it, and the step of applying the cover wall over the open side of the housing comprises applying the cover wall so that the port is approximately adjacent the first portion of the foam in the interior space of the housing.